1. Technical Field
This invention in general relates to computer I/O devices. More specifically, this invention relates to separating I/O devices from a system unit and connecting them through a network such as a local area network.
2. Description of the Related Art
Conventional I/O devices are connected to a host computer through device controllers attached to a system bus internal to the host computer. For example, a monitor is connected to the system bus through a video card, a keyboard through a programmable peripheral interface (PPI), a floppy diskette drive through a floppy drive controller, and a mouse through a serial port. A CD ROM drive is connected to the system bus through an IDE controller or an SCSI controller depending on the type of the CD drive. A hard disk is connected to the system bus through an IDE or SCSI controller depending on the type of the hard disk drive. These controllers for I/O devices are attached to the internal system bus either in a single chip or as an add-on card. Printers are usually attached to the host computer through a parallel port, but sometimes connected to the host computer through a local area network (LAN) such as Ethernet.
Since I/O devices are typically connected to the host computer through device controllers attached to the system bus, the users must be located in the physical proximity to the host computer to access the I/O devices, such as a keyboard, a mouse, a monitor, a floppy diskette drive, or a CD drive. As a result, the users often experience noise and heat from the host computer, and a lack of space due to the space occupied by the system unit. These problems may negatively affect the quality of the work environment and the job efficiency, especially when more than one system unit are used in the work place.
Since each I/O device is tied to one of the host computers, if there is a problem with any of the host computers, the user of the host computer with the attached I/O devices cannot access another host computer without bringing in a new computer. Further, if there is a problem with any of the I/O devices, the user of the I/O device may not be able to use the whole system, and may be required to replace the whole system.
Since the I/O devices are physically attached to the system unit and receive power from the power supply of the system unit, the host computer needs a high-capacity power supply that cause the problems of heat, noise and occupying space. For example, if the power supply and the device controller are close spaced, the power supply may cause noise in the controller, especially in a multimedia controller for high-quality audio or video.
Therefore, there is a need for physically separating I/O devices from the host system and connecting them remotely to the host system.
There is a client/server technology where a client having a CPU, memory and I/O devices is located remotely to the host system. However, the technology does not provide to a solution to the need of physically separating I/O devices because the technology concerns function division between a server and a client by having the server provide the client a function that the client does not have. I/O devices interface with the client and are still attached to the system unit of the client directly.
Printers are sometimes separated from a particular host and connected to the host through a network. But such technology is limited to a printer. What is needed is a general interface that allows all I/O devices such as a keyboard, a monitor, a mouse, and a floppy drive to be separated from the system unit and to be connected to the system unit remotely.
There is the USB (Universal Serial Bus) technology that allows various I/O devices to be connected in a serial bus. It is aimed at improving a conventional system where low speed I/O devices are connected to a system bus such as an ISA bus although the I/O devices are much slower than the CPU and memory. The USB technology, however, cannot dynamically change the connection of the I/O devices. Furthermore, the USB cable is limited to a maximum of 5 meters in distance making it impossible to separate the I/O devices from the host computer system unit. In sum, the USB technology is not a technology to separate I/O device from the host system unit, rather a serial system bus technology of performing efficient I/O.
There is a technology to share I/O devices. For example, a set of a keyboard and a monitor may be shared by several PCs. But the connections between the I/O devices and the system units are usually fixed without providing the ability of dynamically connecting to any host of the host systems at any time. Especially, the I/O sharing technology does not provide the separation between hard disks from the system units.
A host computer may be connected to several terminals using a multi-drop serial line or modem or a telephone line. These connections are fixed connection, lacking the ability of selectively making connections and canceling connection.
Therefore, there is a need for a technology that separates I/O devices from the host system unit and to connect them to the host system unit dynamically.